The basic problem with most pressing tools is the amount of force required for operation. For staplers, the problem is pushing the stapler down and stapling papers together. When using a standard stapler on a tabletop, users typically must reorient their arms to accomplish this task. While ergonomically flawed, this force is needed to push the staple through multiple sheets of paper and to cinch the staple shut. Many users address this problem by using the stapler in a handheld manner, using forearm muscles to actuate the stapler. This method is somewhat adequate for a few sheets of paper. But when more sheets are stapled together, the force required is too great and users typically return the stapler to the table, stands up and pushes down the stapler using full body weight. Considering the stapler is such a ubiquitous device, a better, more ergonomic solution is long overdue.
There are three general categories of solutions to this problem. First are electric staplers, second are staple-gun-style desktop staplers, and third are leverage-type staplers.
The first solution, the electric stapler, provides power so strength is no longer an issue. Foremost among the drawbacks of the electric stapler are higher costs, the need for electricity, and the cord.
The second solution, the staple-gun-style desktop stapler, patent U.S. Pat. No. 5,356,063, is manually powered. This eliminates the need for cord or power source. It uses the staple gun approach of loading and suddenly releasing a spring to drive in a staple. This is a time-proven approach, but it has five shortcomings.
A) Like the electric stapler, it fires a staple. This means it has the same problem of being loud and very sudden.
B) The second problem is that maximum spring loading force is required whether two pages or twenty pages are being stapled. This requires users to input the maximum force every time and gives no control over the impact level on the staple.
C) Another problem is that its spring mechanism makes it taller than an ordinary stapler.
D) The mechanism is not as scalable, preventing the staple gun from being made into a small, inexpensive stapler. For example, standard existing staplers come in inexpensive small-scale versions that are only about three inches long and an inch tall.
E) The last problem is that the spring mechanism tends to weaken over time.
Leverage
The third solution, using leverage to improve a stapler, comes in two basic forms. One is simple leverage; the other is compound leverage.
The simple leverage stapler just extends a handle beyond the point where the staple exits. This would be considered a second class lever because the input of force is at the end of the lever while the output is in the middle of the lever. A common variation has an extending handle that pivots off a different axle than the stapler's axle. The problem with these solutions is that the stapler must be quite large in order to get a substantial increase in leverage. The simple lever staplers are suitable for copy room or specialized uses, but are too large to be used as desktop staplers.
Simple Leverage
The patent, U.S. Pat. No. 6,179,193 by Mikio Nagai, is a good example of the simple lever stapler. It's worth noting that the handle on the Nagai patent almost looks like a compound lever, but it's not. It pushes down directly onto the staple it's firing and not onto the top of the stapler. Accordingly, the frontmost of the two lever pivots must be located directly above the staple to be fired. Hence a substantial portion of the lever must stick out in front of the stapler.
Because it sticks out beyond the point of stapling, the simple lever has another disadvantage: it blocks visibility of the area being stapled. This is particularly problematic in staplers that are not tall. The less vertical distance between the simple lever and the staple cinching anvil, the more the view is blocked. The Swingline model 3786x stapler by Acco Brands Inc. is a prime example of this problem. {No patent number}
Compound Leverage
The second method of improved leverage is the compound leverage stapler, which involves two levers interacting with each other. The first lever is the stapler assembly itself, a third class lever with the output and fulcrum on each end and the input in between.
The second lever is a second class lever with the input and fulcrum on each end and the output in between. The output from the second lever becomes the input into the first lever, creating a compound lever. The fulcrums of both levers connect to the stapler's base.
Compactness is a major advantage of using a compound lever. It allows the second lever to stay within the length footprint of the stapler, by putting its output behind the point of stapling.
There are four relevant patents disclosing the use of compound leverage for stapler operation: GB853,556, GB792,108, U.S. Pat. No. 6,550,661, and JP2004,209,619.
GB853,556 & GB792,108
The first two, GB853,556 and GB792,108 are holders designed to hold an existing stapler. The most significant flaw with these two patents is that the push levers pushes to the back of the stapler, causing three problems: 1) The activation forces are away from the actual stapling operation, making the stapling operation more awkward and unstable; 2) Users, expecting to push down on the front of the stapler, must rehabituate themselves; and 3) The back is more difficult to reach. Additionally, the holders cost nearly as much to make as the staplers, must be stapler specific, and result in a larger and bulkier solution. Furthermore, both staplers confine the lever pivot point to the front of the stapler, in order to in order to open the holders and remove the staplers. This limits the design potential.
Aoki U.S. Pat. No. 6,550,661
The Aoki U.S. Pat. No. 6,550,661 patent shows improvement over the previous patents in that the compound leverage system is a permanently integrated part of the stapler and has a push lever that pushes down in front. However, it has a very serious flaw, a rotationally supporting shaft 16 and a pin 17 are too close to the axle 8 at the rear of the stapler. Because of Aoki's use of compound leverage, this creates a huge concentration of force on shaft 16 and pin 17. This large force creates two problems.
The first problem is that the concentration of force causes disfigurement of the pivot points and cam surfaces. A second problem is a significant increase in friction. The third problem is that smaller movements require greater precision and higher tolerance manufacturing.
The catastrophic combination of increased force with smaller, more precise movement, means the mechanism does not run smoothly; is much more difficult and expensive to manufacture; is more prone to malfunction, and wears out sooner.
Another problem with the Aoki stapler is opening it. Because the pin 17 is permanently trapped in the elongated hole 18, Aoki has created an engaging groove 15 that allows the handle member 5 to release from the rotational supporting shaft 16. However, this increases the mechanical complexity, costs, and increases the chances of mechanical failure. It also makes access more difficult for users because the driver arm 3 has to be in the proper angular orientation for the rotation supporting shaft 16 to disengage and reengage with the engaging groove 15.
Finally, the stapler can be opened to insert new staples but it appears that it cannot be used to staple in the opened-up tacking configuration used, e.g., to staple at a sheet of paper to the wall. The rotational supporting shaft 16 would interfere with the upward rotation of the magazine member 2.
Patent JP2004,209,619
Patent JP2004,209,619 is the fourth example of compound leverage staplers. It suffers the same problem as the Aoki patent U.S. Pat. No. 6,550,661. It does not move the lever's axle far enough forward, away from the staple axle.
However, it is attempting a somewhat different objective: it wants to center the pushing force in the middle of the stapler. Thus the handle has to be near the center, putting the lever fulcrum and pivot at the rear of the stapler. Rather than focusing on the reduction of operating force, this design creates a dome shape to accommodate the palm of the hand. This allows users to push harder, i.e. increase the operating force.
The problems with the JP2004,209,619 patent are many. It does not achieve significant, if any, mechanical advantage. There is considerable stress on the lever fulcrum and pivot. It's much bulkier and has a larger footprint. Its support walls on each side of the base are long and, accordingly, its paper access slot is very short. It does not adapt well to being used as a hand-held stapler.
The following is a brief overview of the patent application disclosure for the mid-zone stapler.